99 Jeep Cherokee Sport, 4.0

I replaced the thermostat and coolant temperature sensor. I also replaced the heavy paper gasket that goes between the thermostat housing and the engine. I cleaned all surfaces well. . The result is a big leak out of the bottom of the housing. So I have these questions :

Does the thermostat have an orientation? Up, down, etc. I pushed it firmly into the hole and thought it was all good. Also, should there be a ring or gasket that goes in the round indentation the thermostat sits in?

Should I have used some sort of sealant or gasket dressing on the thermostat housing gasket to that it seals better? I put it in with nothing on it assuming that the pressure from the tightened bolts makes a seal.

Thanks.

 

The thermostat only installs in one direction with the rod going into the engine. As far as rotation, it doesn't matter, but only one side can face forward. This way the ring in the block seats the thermostat. Sometimes scraping the housing makes it so that it won't seal well with the new gasket because it is soft aluminum. Fel-Pro states to not apply any liquid gasket on the hard gasket. I agree with that.

I hope that this information helps.

 

I understand what part of the thermostat goes into the engine and which part stick out into the thermostat housing. But the thermostat can spin around in a circle. Is there any part of it that is supposed to be at the 12o'clock position?

 

My understanding is that some thermostats come with a bleed hole. If so it should be at the 12 o'clock position.
If not then it does not matter.
Cause of the way it is set up sometimes the thermostat can slip down. You don't realize it and tighten the housing.
This can cause it not to seal properly, obviously, and worst case scenario you can crack the housing.
So I would go buy a FelPro gasket, pull it all apart, check the housing, check that you did clean it up all nice nice, and put it back together without any gunk.
I just did a water pump and I also bought a new thermostat housing just to be safe. Opted to not use the supplied gaskets and went with FelPro's. Checked around online and FelPro is very adamant about
not using any gunk.

 

As Gat said, the orientation doesn't matter (unless it has a bleed hole, that faces upwards). The casting is soft, so you could very well have cracked it without realizing. The first time I replaced my thermostat housing, I didn't notice one of the clamps slightly interfered with the housing until I cracked it while tightening down the bolts. New housing, and lesson learned for me.

You should probably remove the housing and inspect for damage. Make sure all previous gasket material is removed as well.

No need for additional gasket sealant. The paper gasket should be fine.

 

I apologize. I meant rotation not "donation" does not matter.

You definitely can use shellack to stick things temporary. That is what Fel-Pro recommends. I'd be comfortable using it to tack the thermostat with two small dots and the same for gasket. Since you had a leak, be open to replacing the housing. It is a fairly inexpensive part because it is just aluminum.

 

You have to look at the t-stat you have. a lot do have a top/bottom. if it has a hole in the "flange" portion, it must be oriented "up".
As for sealant... some say not required...but for a little added measure, I use a little RTV gasket sealer...not the black, but the gray sealer. Did my water pump and t-stat with housing year and a half ago, no issues.
I'd also recommend some teflon tape on the temp sensor before you put it back in as well.
Did you replace the t-stat housing or just clean it up?.... it's always best to just replace it along with a new t-stat. They are cheap and over time the mating surfaces can become corroded and have tiny pits in the surface leading to leaks too.

 

Been there, done that. As others have mentioned, use something to make sure the thermostat is stuck in place before putting the housing on. No matter what I did, it would slide out of the indentation and leak when I tightened it. Put a small dab of RTV to hold the thermostat in place and no more leaks.

 

Do I need a ring around the thermostat when I put it back in.

 

I use thermostat sealant instead of the paper gasket. I've had those leak immediately after install on multiple occasions and gave up on them. Permatex makes a thermostat housing sealant specific for that application that works much better IMHO.

 

Not a fan of the pressed paper gaskets either. I will at least give them a thin wipe of silicon first.

 

When I did my water pump and thermostat I ditched the supplied paper gaskets for FelPro ones.
No gunk.
Worked out great for me.

 

Proper quality gasket and a thin smear of sealant.

 

It's possible that the thermostat housing is warped. It may not be flush and so there is a small gap between mating surfaces. I'd check for that.